Vehicle braking system



May 19, 12942. A. M. woLF 2,283,713

VEHICLE BRAKING SAYS TEM Original Filed April l5, 1955 mmf BY .2 .i

ATTORNEY.

Patented May 19, 1942 YUNITED STATES PATENT OFFICE Y VEHICLE BEARING SYSTEM Austin M. wolf, Plainfield, N. J. original application April 15, 1933, serial No.

666,332. Divided .and this application May 29, 1939, Serial No. 276,348 Y a1 claims.

This invention relates to vehicle braking systems having certain novel characteristics capable of practical application to either dirigible or rail-borne vehicles. The subject matter ofthe present application constitutes a division of my pending'application for patent, led April l5, 1933, Ser. No. 666,332, now Patent No. 2,181,161, November 28, 1939.

One of the principal objects` of the invention is toprovide a method and means for controlling vehicle brakes, embodying means, automatically responsive to brake application for regulating the braking system to control the rate of deceleration which is variable in accordance with changes 4or variations in the intensity of brake application.

More particularly, I provide a regulating means for vehicle braking systems which is responsive to the combined influence of multiple factors, co-existing at the moment of brake application, to control and modify Ythe rate of deceleration. In one mechanical` embodiment, these factors may comprise speed and inertia responsive means operatively connected with the regulating means for the braking system.

An additional object of the inventionV is to provide a movable inertia mass, responsive to either positive or negative acceleration of the vehicle, with adjustable means for controlling the movement of said inertia mass, and the consequent rate of deceleration.

The present invention provides a new method of control for yvehicle braking systems, and in one embodiment thereof, I propose a coordinated control of both the suspension and braking systems of the vehicle whereby the rigidity of the suspension system and the intensity of braking pressure is modied in response to the combined influence of vehicle speed and deceleration at the moment of brake application. 1

It is also another important object of the invention .to provide in connection with a brake applying means for front and rear sets of vehicle wheel brakes a device which will be sensitively responsive to grade inclination'of the vehicle and which is connected witha part of the brake applying means to actuate the' sameand maintain an effective pressure on 4one set of brakes, independently `of actuation of voperator controlled means releasing the pressure on the other set of brakes.

A more specific object of the invention is to provide means for yieldably opposing movement of the inertia responsive element, with means for regulating and conditioning said yielding means (C1. lss-1o) automatically in accordance with the intensity of brake application, to apply a variable opposing force to the movement of the -inertia yelement from its normal position.

4A further-specific object of the invention resides in the provision of a plurality of Vsprings mounted and arranged'so as to sequentially oppose the movement of said inertia responsive element. y

With the above and other objects in view, the invention consists in the improved vehclebraking system, and in the form, construction and "relative arrangement of the various parts" thereof as will be hereinafter more fully described, illustrated in the accompanying drawing and subsequently incorporated in the subjoined claims. f

,Referring in detail to the drawing in which I have disclosed a particular mechanical embodiment of the invention and in which similar refs erence characters designate Vcorresponding parts throughout the several views:

Fig. 1 is a plan view of a vehicle frame or chassis h'aving* the present invention applied thereto.

Fig. 2 is a semidiagrammatic side elevation with parts show n in section, illustrating the'inlongitudinalside' rails 5 and 6 respectivelya front axle 'I with the wheels 8 and Sand a rear axle vI0 with its wheels II and I2. The brake drums indicated at I3, I4, I5 and I6 are secured to the respective wheels in the usual manner and -'conventional braking mechanismv vis mounted .within these drums. In the present instance, this mechanism is mechanically actuated through the flexible connections I'I, I8,'I9 and 20 respectively, though it will be' understoodv that such connections may also supply pressure fluid to brake actuatingk cylinders mounted within the wheel drums. In the mechanically operated type Vas herein shown, rods 2|, 22, 23 and .24 actuate flexible cables within the connections I1, I8, I9 and 20 respectively. The rods 2| and 22 are operatively connected with lever arms on the ends of a front cross-shaft 25 and the rods 23 and 24 are similarly connected with lever arms on the ends of a rear cross-shaft 26, said shafts being journalled in suitable bearings mounted on the side rails and 6 of the frame.

While I have shown a four-wheeled vehicle, it will be apparent as the description proceeds, that the invention is applicable as well to, railway or other multiple wheeled vehicles. Should two or more rear axles be used, the cross-shaft 26 will apply the initial pull on the braking mechanisms of the rear wheels. Similarly, when two or more front axles are used shaft applies the initial pull to the front braking mechanisms. Also, of course, independent wheel suspension may be employed without affecting the operation of the invention.

In Fig. 2 of the drawing, I have diagrammatically illustrated the engine or prime mover 21 provided with an air-compressor 28 connected by pipe 29 with a storage tank or reservoir 3|).` The pipe line 3| connected with said reservoir has a control valve 3|' located therein, operated, through suitable connections (not shown) by a hand or foot actuated member of conventional form.

The pipe line 3| supplies uid under pressure from reservoir 30 to the branch pipe lines 32 and 33 respectively, said branch lines in turn supplying the pressure uid to the cylinders or diaphragm units 34 and 35 respectively, which actuate link rods 36 and 31 connected with arms 38 and 39 on the cross-shafts 25 and 26 respectively. In place of the cross-shafts 25 and 26 and actuating connections with the brake mechanisms, cylinders 34 and 35 can be mounted, singly or in pairs, on the vehicle axles with t e customary flexible connections between the the distribution of uid braking pressure between f the front and rear wheels of the vehicle. In one embodiment of the control mechanism the branch pipes 32 and 33 are connected by a casing or housing 40. Within this casing the valve 4| is longitudinally slidable and is provided with ports or apertures 42 and 43 respectively, located near the opposite ends of said valve. The distance between these ports or apertures is less than the distance between the branch pipes 32 and 33 so that in all positions of the slide valve said ports will be out of alignment or in staggered relation to the pipe connections 32 and 33 with the casing 40. As shown, in the normal position of said slide valve, the ports 42 and 43 have an equal area communicating with the respective branch pipes 32 and 33 so that when valve 3| is actuated, brake operating uid of equal volume and pressure is applied to each of the cylinders 34 and 35.

Of course, this initial fluid pressure supply whereby the brakes are rst actuated, may be sensitively controlled by the operator in the actuationof valve 3|'. When traveling at low speed, valve 4| may remain substantially in its normal position while the brakes are applied with suicient intensity to completely stop or arrest movement of the vehicle.

However, it is well known that when the vehicle is moving at reasonably high speed, and the brakes are suddenly applied, equal distribution of the braking effort between the front and rear Wheels does not give satisfactory performance. In order to compensate for the shifting of the weight of the vehicle body with an increasing proportion on the front wheels during negative acceleration, it is recognized, in current practise, that greater braking effort should be applied to the front wheels than to the rear wheels. However, with increasing speeds, this proportional distribution should vary in order to obtain the most efficient braking action and bring the vehicle quicklyand smoothly to a stop at such high speeds. Therefore, I have provided means for automatically varying this distribution of the braking pressures between the front and rear wheels in response to deceleration, which of course, varies in eiect with variation in vehicle speed and the intensity of initial brake application.

In my present invention, this desirable automatic control is obtained by the use of a movable inertia responsive mass 44 connected with a rockable arm or member` 45 fulcrumed as at 46, within the housing or casing 41. This connection between mass 44 and the arm 45, in the present instance, comprises a rod 48. Intermediate of its ends this rod is pivotally connected with a sleeve 49 on one end of a rod 50 slidably mounted in a suitable bearing 5| on the wall of the housing 41. On the opposite wall of said housing an adjustable stop 52 is suitable mounted to be engaged by the end of sleeve 49, whereby swinging movement of the inertia responsive mass 44 and rocking movement of arm 45, may be variably and positively limited.

The inertia mass 44 and arm 45 are yieldingly held in a normal centered position within the casing 41 by means of the springs 53 and 54, respectively mounted in cup members 55 and 56 which are removably threaded in bosses or extensions formed on the opposite walls of the casing 41.

In addition to the above described inertia responsive means for controlling the operation of the regulating valve 4|, I also provide a speed responsive means concurrently operable with the inertia means to modify the regulatory eiect of the latter. This speed responsive means may consist of a conventional type centrifugal governor 51 driven by `shaft 58 and which actuates the bell-crank lever 59 having a fixed pivot at 59'.

To the end of slide valve 4| projecting from casing 4|), a vertically disposed equalizer bar 6U is pivoted intermediate of its ends as at 6|. This bar at its upper end is pivotally connected as at 62, with the slidable rod 50 actuated by the inertia reesponsive mass 44. A link 63 has one of its ends pivotally connected at 64 with the lower end of the equalizer bar while the other end of said link is pivotally connected as at 65 with one arm` of the bell-crank lever 59.

Assuming now that the vehicle is traveling at high speed and that the operator actuates valve 3|' to apply the brakes, the initial intensity of the brake application by the distribution of equal uid pressures to the front and rear brakes is. of course, dependent upon the extent or degree of opening movement of the valve 3|. Upon the initiation of braking torque reaction on the wheels resulting in deceleration of vehicle speed,

vthe inertia mass 44 leaves its central position indicated by the line A, and assumes a position substantially as indicated, for instance, by the line B, Dependent upon the severity of the braking torque reaction, this swinging movement of the inertia mass against the opposed resistance of spring 54 may continue until the sleeve 49 strikes the adjustable stop member 52. This movement of the inertia responsive element is transmitted through the connected rod 50 and bar 60 to the slide valve 4I', said valve being moved towards the left from its illustrated position to place port 42 thereof in increasing alignment with the branch uid supply pipe 32 and at the same time effect an increasing misalignment or cut oi in the fluid supply connection between port 43 and branch line 3'3 to the rear wheel brakes. Therefore, due to this variation in the eii'ective areas between ports 42 and 43 and branch lines 32 and'33 respectively, a greater amount of pressure fluid will be supplied to the actuating cylinder for the front brakes. As the brakes are initially applied by the manual operation of valve 3|' with more or less intensity, the inertia mass 44 will correspondingly and progressively -move in the forwarddirection indicated by line B, until it reaches a stablerposition, such position, and therefore, the positions of the ports in Valve 4| with respect to pipe line's 32 and33,

being determined by the extent or degree lof braking torque reaction andthe initial deceleration effect consequent thereon. Of course, any

lchange in the intensity of braking pressure, ef-

fected by adjustment of the valve 3|', will necessarily result in a variation in the rate of deceleration. As the vehicle slows up, the `inertia mass 44 will swing back towards its normal or central position and finally assume the position indicated by the line A, at very low speed and when the vehicle is at rest.

The influence of this inertia responsive device upon the position of the regulating or modulating valve 4| will be modified by the conjoint action of the speed responsive means. It is obvious that at high driving speed the centrifugal governor 51, operates through the link connection 63 with the equalizer bar 60 to shift the valve 4| to the left, independently of any movement of the inertia influenced mass 44. either increase in vehicle speed or in inertia effect will result in the above described operation of the regulating valve 4|, and in which either of these controlling influences upon the operation of the regulating valve is automatically compensated for by the equalizer 60.

The valve ports 42 and 43 may be of any selected size and cross-sectional shape to obtain a desired predetermined graduated lcontrol of the fluid braking pressures.

By making the springs 53 and 54 very flexible, the apparatus can be made sensitively responsive to grade inclination, aswhen the vehicle is ascending or descending a hill. Assuming that the vehicle is moving on an ascending grade, the inertia mass 44 will assume approximately the position indicated by the line C, resulting in a vmovement of the control valve 4I to the right or rearwardly whereby the brake applying cylinder 35.wi1l receive the pressure fluid in increasing volume upon actuation of the valve 3|'. Of course this operation of the valve 4| would also be modified in accordance with the speedV of movement of the vehicle, the speed responsive device through the equalizer bar connection tending to move the valve 4| "toward the left. Therefore if the speed of movement of the vehicle on the up-grade increases, there is a progressively increasing movement of the valve 4| towards its normal position, notwithstanding the This would be very desirable on heavy buses or trucks.

On approaching a descending grade, valve 3|' is operated to provide approximately equal pressures on both the front and rear brakes. When` inertia weight 44 moves to position B and shifts control valve 4|', the supply of pressure uid to the rear cylinders 35 is'cuton', while the supply to the front cylinders 34 is increased, .If it becomes necessary to park the vehicle on the grade, the, pressure on the rear brakes will thus be maintained after the operators controlvalve 3| returns to normal position so that the connec tions with the front brake cylinders 34 are vented through said valve.

In order tomake the means which yieldingly resists the operation of the inertia responsive device progressively variable in proportionate ratio with variation in the intensity of brake application, 1 provide the arrangement shown in Fig. 3 of the drawing. Thus, instead of the single spring opposing movement of the rocker arm 45 in each direction, I provide an outer relatively flexible spring 66 of large diameter and an inner comparatively stiff and shorter spring 61. These springs at their outer ends are suitably attached to the base wall of the cup member which has a quick acting external thread engaged with the internal thread of the boss 41' on the wall of the housing 41. The inner end of the longer spring 66 is at all times' in bearing engagement against one side of the rocker arm 45 while thev corresponding end of the shorter inner spring 61 is outof contact with and spaced from said arm when in its normal position. It will thus be understood that this dual spring arrangement results in the sequential application of yieldable opposing pressures by the respective springs to the swinging movement of the inertia operated rocker arm 45. Of course itis evident that this yielding resistance to the movement of the arm progressively increases with increase in the inertia force.

However, I also provide means for automatically conditioning said springs whereby such progressive increase in the opposing stresses of said springs may be regulated or variedin accordance with variations in the intensityrof brake application. To this end, I employ asuitable motor means for adjusting the threaded cup 55" -relative to the center line of the housing 41. As

herein shownfthis motor means comprises a'suitable cylinder indicated at 68, having a piston or diaphragm operating therein, suitably connected as at 69 with a rod or lever 10 connected tothe outer end of the cup 55'. Thecylinderi is supplied with pressure fluid through pipe 1| connected with the fluid pressure supply pipe 3| between valve 3|' and the branch pipe lines 32 and 33. It is thus apparent that if the valve 3| is opened and pressure established in the line 3|, such fluid pressure will also be supplied to cylinder 58, thereby actuating lever 10 and rotating the cup l55 to move the same inwardly and thereby cause the sequentially acting springs 66 and 61 to apply an increased opposing resistance to the swinging movement of the rocker arm I5, and accordingly to the sliding movement of valvevll. Thus in proportion to the increase of pressure in pipe line 3l and the intensity of brake application, the opposing resistance to the action of the inertia device and movement of valve 4|A is also increased. The rate of deceleration is thus controlled and varied so that in the operation of the braking system, even at very high traveling speeds, the vehicle will be quickly and smoothly brought to a stop. It is of course, understood that the arrangement of the springs 66 and 61 and the automatic regulating or adjusting means therefor is duplicated at the opposite side of the housing 41 as indicated by Fig. 2 of the drawing.

Power may be transmitted by any suitable means to shaft 58 for the operation of governor 51 and in Fig. 4 of the'drawing I have shown said governor arranged at the rear of transmission unit 12, the shaft 5B being driven from the universal joint shaft 13 by the conventional bevel gears 14. In this view, I have shown the slide valve 4| for the control or regulation of the braking pressures actuated through bell-crank lever 59 and connecting link 63', only in response to the operation of the centrifugal governor. l

In Figs. 1 and 2 of the drawing, I also show the vehicle suspension system coordinated with the braking system for simultaneous regulation and control by the inertia and speed responsive means above described. Thus the cross-shaft 15 is suitably journaled at its opposite ends upon the side rails 5 and 6 of the vehicle frame and adjacent each of said ends is provided with upwardly and downwardly extending arms, indicated at 16 and 11 respectively. This shaft, at its approximate center is further provided with the upwardly extending arm 18 pivotally connected with a longitudinal extension 19 on one end of the slide valve 4l.

Upon opposite ends and at opposite sides of the vehicle frame, the front and rear shock absorbers 80 and 8l are suitably mounted. These shock absorbers may be of any desired conventional type and are each provided with a suitable control valve for the shock absorbing liquid. These valves are actuated and adjusted through the rod connections 82 between the valves of the front shock absorber and the arms 16 on shaft 15 and the similar rod connections 83 between the rear shock absorbers and the arms 11 on said shaft. It will thus be apparent that as the braking pressure is automatically controlled and varied in the manner above explained, the action of the shock absorbers to yieldingly resist movement of the vehicle body relative to the wheel axles will be correspondingly regulated or varied.

From the foregoing description, the construction, manner of operation and numerous advantages of my improved vehicle braking system will be clearly and fully understood. It will be seen that such a mechanism will be efficiently and accurately responsive in its operation and will automatically govern and control the differential application of the brakes to the best advantage, and as required in order to nullify the undesirable effects of a plurality of variable factors incident to the operation of the vehicle,

and over which the operator has -no control.

I have herein referred to the use of compressed air as the power medium for operating the brakes. It will however, be apparent that by the substitution of equivalent mechanical units well known in the art the characteristic features of my present disclosure are applicable as well to hydraulic or vacuum operated brakes. Further, although I have disclosed my invention as applied to an automotive road vehicle, it is self-evident that the same may also be utilized to advantage in connection with the braking system of rail-borne vehicles. Likewise, in such case, the proper equivalent mechanical units commonly used in this art would be substituted for the corresponding features of my present disclosure.

Therefore, it is accordingly to be understood that in the further practical development of my present invention and in its application to various types of vehicles, I do not consider myself as limited to the particular mechanical embodiment of the apparatus herein illustrated, but reserve the privilege of adopting other structural forms of the several mechanical units as well as variations in the relative arrangement of such units, as may fairly be considered as incorporated Within the spirit and scope of the appended claims.

I claim:

1. In combination with vehicle braking means and a brake pressure regulating member therefor; independently operable devices directly coacting with said regulating member and jointly responsivel to the combined influence of brake application and vehicle speed, to control the operation of said regulating member.

2. In combination with vehicle braking means and a brake pressure regulating member therefor; a combined speed and inertia responsive means connected with and controlling the operation of said regulating member. Y

3. In combination with vehicle braking means and a single brake pressure reguating means therefor; controlling means connected with said regulating means, comprising an inertia device responsive to vehicle deceleration and a device responsive to vehicle speed, said devices conjointly and independently actuating said regulating means.

4. In. combination with regulable device for vehicle braking systems, means automatically responsive to vehicle deceleration connected to regulate said device, and means responsive to vehicle speed connected toregulate said device independently of said first named regulating means.

5. In a wheeled vehicle having a chassis supported for movement relative to the vehicle wheels; brake mechanism, means for variably regulating the braking force of said mechanism, means operatively connected with said regulating means and responsive to relative displacement between the vehicle chassis and wheels, and means responsive to vehicle speed controlling the effect of the operation of said last named means.

6. The combination of regulable braking means for a vehicle, and controlling means therefor comprising an inertia device responsive to vehicle deceleration connected 'to regulate said braking means, and a device responsive to vehicle speed connected to modify the regulatory.

effect of said inertia device.

7. In combination with regulating means for a vehicle braking system, a movable inertia mass operatively connected with said regulating means, yielding means resisting movement of the inertia mass, and means operatively connected in the braking system for varying the resistance offered by said yielding means in accordance with the intensity of brake application.

8. In combination with regulating means for a 2,283,713 uid operated.. .braking` systexril a` rnc'ivable inertiay i mass operatively connected with saidregulatlng means, yieldable means resisting Vmovement of saidmass. from its' fnormalposition, and fluid yieldable means t'o such movement.

operatedmeans forvary'j gthe resistance of said f 9. In combination With'a vehicle braking sys-f tem, a retardation controller device having air element movabl'eaccording to4 the" rate of reftardation of the vehicle, yielding meaiisfor op posing movement of said element, regulating means for conditioning said yieldingjmeans to oppose movement Ofsaid elementwith variable` forces, and means connected withand operative; ly controlling said regulating means.` f

10. In .combination tem, a Vretardation controller'devicehaving 'Y an with ra Vehicle'braking syselement movable according to the rateof rel tardation of the'vehicle, yielding means for op 1 posing movement of saidy element, vregulating means for conditioningv said yielding means'to opposemovementof said element with; variable forces, and means automatically'respon'sivefupon operation of the vehicle braking system, to oper atively `control said regulatingl means.

11. vIn combinationwith a' fluid 'operated've-V hicle braking system, alretardation controller de` vice having an elementv movable according to the rate of retardationl o f the vehicle, yielding means for. opposing movement of said element; regulat ing means for conditioning said yielding meansA to oppose movement of said elementwith variable forces, and means responsive to the influence of Y fluid pressurein the braking system to operative- 13. An inertia control for brakes comprising a movable inertia mass; brake controlling means operable by motion thereof; yielding means resisting such motion; and means responsive to the intensity of brake applic-ation for varying the resistance offered by said yielding means.

14. The method of controlling vehicle brakes,

which comprises regulating the intensity of brake application in response to the initial deceleration produced Iby such application, to change the rate of deceleration; and modifying such deceleration rate in response to change of the intensity of brake application.

l5. 'Ihe method of controlling the operation of a vehicle braking system having brake pressure regulating means, which consists in controlling the operation of said regulating means by force generated by movement of the vehicle, and modifying the effective effort of such force to actuate said regulating means, in response to variation in the intensity of brake application.

16. The method of controlling the operation of vehicle brakes, which consists in controlling the operation ofthe braking system by inertia forces incident to deceleration resulting from brake application, and modifying the eiective controlling effort of such inertia forces in'proportionate ratio to changes in the intensity of brake application.

17. The method of controlling the operation of vehicle brakes which comprises controlling the operation of vehicle brakes in response to the deceleration produced by said application, and

modifying the effect of such response in accord- 75 "tion, a'commu'ni'cation ance with vehiclefspeed to lchange the rate of deceleration; f

18'. The method of 'controlling the operation of vehicle brakes which 'comprises' regulatingthe intensity of'b'rake application independently of f volitionaloperator control and in response to the by such brake application, i K and'modifying such response in accordancewitlideceleration produced variation` of thefoperator controlled intensity 'of brake application; Y

of the :vehicle in response' to brake' application,-

which consists'in controlling the operationvof the braking system" by in celera .tion,`andv modifying the enectiveeffort of suoli ertia.` force's`,'upon variation in jftheintensity of brakeiappication', tocorrespondingly thev brakes, a; retardationcoritroller device for y means effective controller device."`

2 1. The metnodfoff' vehicle suspension" and braking systemsjwhich' @mists in' Simltane'ousli'modifyiiignie 'rigidity' y afflf'ldf` the" intensity of braking pressure 1n response to thefco'mbined inof the suspension system mi-ence or yehiciefspeedaiidj 'deceleration at the moment of brake applica 22-.In combination with 'a vehicle suspension ion system having modifying means and a. braking system having brake means responsive to the combined inuence of the inertia eect of deceleration and to vehicle lspeed at the moment of brake application to actuate said brake and said modifying system.

2 3. I n combination with avehicle having brakg means and a fluid shock absorber having resistance regulating means; means responsive to the combined influence of vehicle speed and the inertia eiTect of deceleration at the moment of brake application to actuate said resistance regulating means and modify the resistance of the shock absorber.

24. In combination with a fluid pressure braking system for'vehicles having front and rear sets of brakes, a source of uid pressure, and operator controlled brake applying means between said pressure source and each set of brakes; and means automatically responsive to grade inclination of the vehicle from the horizontal and cooperating with a part of said brake applying means to maintain eiective pressure on one set of brakes, independently'of operator control of pressure on the other set of brakes.

25. Incombination with a fluid pressure braking system for vehicles having front and rear sets of brakes, a source of fluid pressure, and operator controlled brake applying means between said pressure sourceand each set of brakes; means automatically responsive to grade inclination of the vehicle from the horizontal and cooperating with a part of said brake applying means to maintain effective pressure on the rear set of brakes independently of the operator controlled pressure supply to the front set of brakes.

pressure regulating means means of the suspension 19. Theme-tirador crnitroiiiiig the dece1eration ertia forces incident "to de`k v cotrbuiiigthe" operandi of pressure regulating means:

26.In control .means for vehicle brakes, a. movable control member, resilient means normally resisting movement of said member` from one position, and fluid pressure responsive means for conditioning said resilient means to variably oppose movement of said member to a second position.

27. In a vehicle braking system, a movable brake pressure control member, an inertia device operatively connected therewith to actuate the same upon deceleration of the vehicle, and means responsive to the intensity of braking pressure to modify the effective inuence ofthe inertia device upon said control member.V

28. In rluid pressure braking apparatus for a vehicle, a plurality of sets of brakes, means for actuating the brakes and comprising a source of pressure, a fluid motor associated with each brake andconduit means for connecting. said motors to the source of pressure. normally open valve means associated with the conduit means leading to the fluid motors ofone set of brakes, and momentum-actuated means automatically operating to close said valve means Vwhen the rate ofv deceleration of the vehicle reaches a predetermined value, said valve means when closed maintaining the existing fluid pressure in the iluid motors of said set of brakesand preventing additional pressure to be applied thereto.

29. In uid pressure braking apparatus for a vehicle, front and'rear brakes, means for actuating the brakes and comprising a source of pressure, a nuid motor associated with each brake and conduit means for connecting said motors to the source of pressure, normally open valve means associated with the conduit means leading to the fluid motors of the rear brakes, and momentum-actuated means automatically operating to close said valve means when the rate of deceleration of the vehicle reaches a predetermined value. said valve means when closed maintaining the existing fluid pressure in the fluid motors of the rear brakes and preventing additional pressure to be applied thereto.

30. In fluid pressure braking apparatus for a vehicle, a plurality of sets of brakes, means for actuating the brakes and comprising a source of pressure, a fluid motor` associated with each brake and conduitmeans for connecting said motors to the source of pressure, and valve means associated 'with the conduit means leading to the uld motors of one set of brakes, said valve means comprising a member normally maintained in valve open position by the action of gravity but moved to a valve closed position by the action of inertia during deceleration of the vehicle at a predetermined rate, said valve when closed. maintaining the existing rluid pressure in the fluid motors of said one set of brakes and preventing additional pressure to be applied thereto.

31.1n combination with a vehicle having brake control means, a sp'eed responsive device, and a fluid shock absorber having resistance regulating means; means co-operatively connecting said .resistance regulating means with the brake control means and speed responsive device and operatively responsive to an eective operation of said brake control means and to vehicle speed to actuate said regulating means and modify the resistance of the shock absorber.

Y AUSTIN M. WOLF. 

